The dynamics of the Cl+n-C4H10→HCl (v′,j′)+C4H9 reaction at 0.32 eV

Rotational state resolved center-of-mass angular scattering and kinetic energy release distributions have been determined for the HCl (v' = 0, j' = 0-6) products of the reaction of chlorine with n-butane using the photon-initiated reaction technique, coupled with velocity-map ion imaging. The angular and kinetic energy release distributions derived from the ion images are very similar to those obtained previously for the Cl plus ethane reaction. The angular distributions are found to shift from forward scattering to more isotropic scattering with increasing HCl rotational excitation. The kinetic energy release distributions indicate that around 30% of the available energy is channeled into internal excitation of the butyl radical products. The data analysis also suggests that H-atom abstraction takes place from both primary and secondary carbon atom sites, with the primary site producing rotationally cold, forward scattered HCl (v' = 0) products, and the secondary site yielding more isotropically scattered HCl (v' = 0) possessing higher rotational excitation. The mechanisms leading to these two product channels are discussed in the light of the present findings, and in comparison with studies of other Cl plus alkane reactions.

Exit interaction effect on nascent product state distribution of O(1D)+N2O-->NO+NO

We have determined the rotational state distributions of NO(v'=0,1,2) products produced from the reaction O(1D)+N2O. This is the first full characterization of the product rotational distribution of this reaction. The main part of each rotational distribution (up to j' approximately 80) has rotational temperature approximately 20,000 K and all these distributions are quite near to those predicted by the phase space theory (PST). This observation and previously reported vibrational distribution indicate that the most part of the energy partitioning of the reaction products is at least apparently statistical although the intermediate of this reaction is not so stable as to ensure the long lifetime. On the other hand, the distributions in the high rotational levels (j'=80-100) are found to decrease more sharply as j' increases than the PST predictions. The origin of the observed decrease of the distribution is discussed with quasiclassical trajectory (QCT) calculations on a five-dimensional ab initio potential energy surface (PES). The observed near-statistical distribution and the sharp decrease in the high-j' levels are well reproduced by a "half-collision" QCT calculation, where statistical distribution at the reaction intermediate is assumed. This agreement shows the rotation-translation interaction in the exit region has an effect of yielding small high-j' populations. However, a little bias of the calculated distribution toward lower rotational excitation than the observed one indicates that the combination of the statistical intermediate and the exit interaction on the current PES does not completely describe the real system. It is suggested that the reaction intermediate is generated with the distribution which is close to statistical but a little biased toward yielding high-j' products, and that the interaction in the exit region of the PES results in the sharp decrease in the high-j' levels.